1. Field of the Invention
The present invention relates to image code transform systems which can arrange moving images of a plurality of small screens to generate a composite large screen image and obtains sequences of small screen coded data corresponding to compressed/encoded data of a plurality of small screens of moving images from a sequence of large screen compressed/coded data corresponding to compressed/encoded data of the composite large screen image and more particularly, to an image code transform system which can obtain desired small screen coded sequences while eliminating the need for expanding a large screen compressed signal.
2. Description of the Related Art
A conventional image data compression apparatus for subjecting a large screen signal created by composing small screen moving image signals to a data compressing operation, for the purpose of minimizing the hardware of an encoding/decoding system, does not respectively independently compress and encode moving images of a plurality of small screens but composes a plurality of moving image signals of the small screens into a single moving image signal of a large screen, and then subjects the large screen moving image signal to a collective compressing/encoding operation to thereby generate and output a coded sequence of large screen compressed/coded data.
In order to extract the compressed/coded data sequences of the small screen moving image signals from the compressed/coded data sequence of the large screen moving image signal thus subjected to the data compressing and encoding operation, a prior art image code transform apparatus first decodes and transforms the large screen compressed/coded data sequence again into the large screen moving image reproduction signal, then separates the large screen moving image reproduction signal into a plurality of small screen moving image reproduction signals, and then subjects the small screen moving image reproduction signals again to the compressing/coding operation to obtain desired small screen compressed/coded data sequences of the small screen moving image signals.
Explanation will next be made as to the above prior art by referring to FIG. 1. The prior art system comprises an image data compression device and an image code transform device.
As shown in FIG. 1, the image data compression device includes a plurality of TV cameras 1a, 1b, . . . ; a multiplexer (MUX) 92 for receiving small screen moving image signals a, b, . . . issued from these TV cameras, composing these small screen moving image signals into a large screen moving image signal, and outputting the large screen moving image signal; and a large screen encoder (ENC-L) 93 for subjecting the large screen moving image signal to a data compressing operation to generate a large screen compressed/coded data sequence and outputting the large screen compressed/coded data sequence. The image code transform device, on the other hand, includes a decoder (DEC) 94 for expanding the large screen compressed/coded data sequence to a large screen moving image reproduction signal; a demultiplexer (DMUX) 95 for dividing large screen moving image reproduction signal into small screen moving image reproduction signals and outputting them; and a plurality of small screen encoders (ENC-S) 9a, 9b, . . . for receiving the plurality of small screen moving image reproduction signals, subjecting the received small screen reproduction signals to a data compressing operation into small screen compressed/coded data sequences A', B', . . . and outputting the small screen compressed/coded data sequences respectively.
More specifically, the plurality of TV cameras 1a, 1b, . . . supply the small screen moving image signals a, b, . . . to the multiplexer (MUX) 92 respectively. The multiplexer (MUX) 92 composes the small screen moving image signals a, b, . . . into the single composite large screen moving image signal and outputs the composite image signal to the large screen encoder (ENC-L) 93. The large screen encoder (ENC-L) 93 subjects the large screen moving image signal received from the multiplexer (MUX) 92 to the compressing and encoding operations into the large screen compressed/coded data sequence for its output.
The decoder (DEC) 94 expands the large screen compressed/coded data sequence received from the large screen encoder (ENC-L) 93 to obtain the large screen moving image reproduction signal, and outputs the large screen moving image reproduction signal to the demultiplexer (DMUX) 95. The demultiplexer (DMUX) 95 in turn separates the large screen moving image reproduction signal received from the decoder (DEC) 94 into the small screen moving image reproduction signals corresponding to the original small screens, and then supplies the separated small screen moving image reproduction signals to the respective small screen encoders (ENC-S) 9a, 9b, . . . . The encoders 9a, 9b, . . . subject the small screen moving image reproduction signals to the compressing and encoding operations to output the small screen compressed/coded data sequences A', B', . . . , respectively.
The aforementioned prior art image code transform system repeats the compressing and encoding operations of the moving image signals twice. This prior art, even if repeating the compressing and encoding process, will not involve any image quality problem, so long as it employs the information-preserving data compression method as its data compression/coding/decoding system. When the prior art employs such a non-information-preserving data compression method as a discrete cosine transform (DCT) which involves real number computation in the coding/decoding process, however, an error takes place in the coding and decoding process and such error is accumulated through such process repetition, thus inevitably resulting in reduction of its image quality. Further, in the prior art system, since the repetitive decoding and coding operations require the decoder and the plurality of encoders associated with the plurality of small screens, this inevitably requires a complex system arrangement.